Question

1.2.3+2.3.4+3.4.5+...+98.99.100

Answer 1

Coi A = 1.2.3 + 2.3.4 +... + 98.99.100

 4A = 1.2.3.4 + 2.3.4.4 +... + 98.99.100.4

 4A = 1.2.3.4 + 2.3.4.(5-1) +... + 98.99.100.(101-97)

4A = 1.2.3.4+2.3.4.5-1.2.3.4 + ... + 98.99.100.101-97.98.99.100

4A = 98.99.100.101

4A =97990200

A = 97990200: 4

A=24497550

Answer 2

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